Orbital Tumors - Pseudotumor

Definition

Idiopathic orbital inflammatory disease "pseudotumor" is a nonspecific inflammation involving the orbit. It is a hypocellular lymphoid lesion, often incompletely replacing the orbital fat, lacrimal gland and extraocular muscles in which mature lymphocytes, plasma cells, histiocytes are seen

Demographics

Males and females are equally affected. Both children and adults could be afflicted by idiopathic inflammations. Most often in middle-aged adults, but also young children and elderly patient . In children, approximately one-third of cases are bilateral. Bilateral pseudotumor in adults is less common and should elicit evaluation for systemic vasculitis such as Wegener's granulomatosis or polyatertitisis nodosa) and lymphoma.

Etiology

The etiology of idiopathic orbital inflammation is unknown. It is believed to be an orbital immune reaction, although no local autoantigens in the orbit have been identified. Possibilities include a blood-borne antigen or antibody localizing in the orbit, which has a rich vasculature.

Signs and Symptoms

The clinical presentation is dominated by inflammatory signs and could be variable. The acute form of the disease is the most striking.

History or prior episodes, orbital CT which shows thickened posterior sclera (or a ring of scleral thickening), orbital fat or lacrimal-gland involvement, thickening of the extraocular muscles. In cases of orbital pseudotumor, bone destruction is uncommon.

Differential diagnosis

The differential diagnosis of orbital pseudotumor includes orbital cellulitis, ruptured dermoid cyst, vasculitis (Wegeners'), lymphangioma, lymphoid tumor, and, in children, rhabdomyosarcoma, metastatic neuroblastoma, and Ewing's sarcoma. In the myocitic subtype, one must also consider thyroid orbitopathy; of note, in thyroid disease, the onset is usually slower, and although asymmetrical, it is often bilateral. Also in the differential in patients with enlarged extraocular muscles are metastatic carcinoma, direct carotid cavernous fistula, spontaneous dural cavernous fistula, and systemic lupus erythematous

Classification of Psuedotumors

Rootman and Nugent classified acute orbital pseudotumors according to their orbital location, and described five patterns: anterior, diffuse, apical, myositic, and lacrimal.

Anterior

inflammation involving the globe and anterior orbit with pain, lid swelling, Ptosis ( Ptosis is sometimes referred to as Blepharoptosis. It refers to an eyelid which is droopy. This could cause a loss of vision, especially while reading, headaches, and eyebrow strain. Please click on the Ptosis page for more details), diplopia, uveitis, papillitis, optic neuropathy, and exudative retinal detachment. CT reveals diffuse anterior orbital inflammation, scleral and choroidal thickening.

Diffuse

inflammation similar to anterior pseudotumor but are more severe. Patients could exhibit more severe papillitis, choroiditis, and optic neuropathy. CT reveals diffuse orbital involvement.

Apical

patients with posterior pseudotumors present with less proptosis, pain, and visible inflammation, but with a tendency toward the early development of optic neuropathy. CT reveals inflammatory process in the orbital apex, possibly extending along the course of the extraocular muscles

Myositic

patients have one or more inflamed extraocular muscles. They often complain of sudden onset of retrobulbar pain, worsened with movement.. CT reveals diffuse enlargement of the extraocular muscle, including the insertion; in contrast, patients with thyroid ophthalmopathy have enlarged muscles, but sparing the insertion

Lacrimal

patients with posterior pseudotumors present with less proptosis, pain, and visible inflammation, but with a tendency toward the early development of optic neuropathy. CT reveals inflammatory process in the orbital apex, possibly extending along the course of the extraocular muscles

Pathology

The histopathologic findings in pseudotumor are variable, depending on where the biopsy was taken and when in the course of the disease it was sampled.

Classically, it is composed of 1) an infiltrate including lymphocytes plasma cells, macrophages, eosinophils, and rarely neutrophils 2) follicular lymphoid hyperplasia within a loose fibrous stroma.

Tissue that is more fibrous is seen in chronic situations. Children could exhibit a heavy eosinophilic infiltrate

Treatment

In various cases, treatment of orbital pseudotumor could be initiated without a preceding orbital biopsy. Initial therapy consists of systemic corticosteroids adjusted for the patient's weight; typically 60- 100 mg/day of prednisone per day. In general, acute cases respond more rapidly than chronic cases and bilateral cases could require a longer course than unilateral disease.

A biopsy (with touch prep) is performed, however, if there is no clinical improvement after treatment with systemic steroids. Once the diagnosis is confirmed, additionally modalities of therapy include orbital irradiation (low-dose supervoltage radiation in the range of 1000 to 2000 rad is given in divided doses over a 10- to 15-day course) (101)., cyclophosphamide, and rarely orbital decompression.